This invention is related to an improved process for making a tufted carpet having high tensile and tear strengths and in which the pile yarn and upper surface of the carpet backing are both dyeable.
Woven and nonwoven sheets of polypropylene are used in the carpet industry as primary backing for tufted carpets. The woven sheets are usually made from continuous polypropylene ribbon filaments which are sometimes fibrillated. The nonwoven carpet backings are made from continuous polypropylene filaments of textile denier. It is well known that polypropylene backings, although otherwise desirable, are not readily dyeable. U.S. Pat. No. 3,605,666, issued to Kimmel et al. on Sept. 20, 1971, is directed to this dyeability problem and discloses a tufted carpet with a compatibly dyeable upper surface made by needling a layer of staple, unbonded fibers onto one surface of a scrim and tufting a yarn through the scrim and the layer of staple fibers. While attractive carpets can be made by the disclosed process, difficulties are encountered when for economical reasons carded webs of low basis weight, i.e., 13 to 30 g/m.sup.2, are used for the layer of staple fibers. These low basis weight carded webs tend to fall apart when handled, provide poor cover, and may even have open holes. In addition, the needling operation greatly reduces the tear strength of the tufted, pile carpet produced from the backing.
U.S. Pat. No. 3,983,028, issued to Cole on May 9, 1961, discloses a tufted carpet made by tufting a yarn through a backing member and a bracing web which are held a spaced distance apart. Suitable bracing members disclosed therein include nonwoven fabrics, woven and knitted fabrics. The tufted carpet is said to have better compressional properties and is more adaptable to dyeing when employing nylon in both the bracing member and pile yarn. The Cole process requires that the tufting machine be equipped with an auxiliary needle plate placed at a desired distance from the conventional needle plate. Commercial tufting machines do not have such an auxiliary plate. Moreover, traditional carpet styles, such as those with low pile height, are not easily made on the modified tufting machine described by Cole.
A need still exists for improved processes for preparing from a polypropylene backing, a tufted carpet having high tensile strength, high tear strength, a readily dyeable pile and a readily dyeable upper surface of the backing.